TIPS WITH TONY: Machining Versus Molding for Magnesium Parts

In our latest tip, we’re talking about magnesium, and how to use it in product design for metal parts that need to be lightweight yet strong.

Magnesium works well for reducing component weight in place of steel or aluminum as it’s the lightest structural metal currently available. This lends itself well to a range of applications in the automotive, aerospace and electronics industries.

It’s heavily used in vehicle lightweighting to lower fuel consumption, reducing automakers overall carbon footprint. It’s also used to create lighter and thinner electronics or simply whenever a lightweight yet strong backbone material is needed in a part. Be sure to test and review magnesium’s material properties closely as it’s not always the proper substitute for other metal or plastic materials.

Magnesium versus




75% lighter

33% lighter

Greater stiffness

Thinner walls

Similar or greater mechanical properties

Improved strength and wear resistance

Consolidation of parts

Consolidation of parts

Higher temperature

Machines faster

Machines faster

Creep resistant

Reduced tooling costs

Improved corrosion resistance

Fewer supports needed

What manufacturing methods are there for magnesium? Proto Labs offers both CNC machining and injection molding for prototype and low-volume mag parts, though magnesium die casting also used in the industry.

How do I choose the right manufacturing method? Quantity, lead time, size and material properties will greatly impact which manufacturing method to use.

CNC Machining
If 200 parts or less are needed, CNC machining is a good choice. Proto Labs mills parts in magnesium AZ-31 metal in 1 to 3 days. Maximum part size for milled magnesium is:

  • 10 in. by 7 in. with a max. depth of 3.75 in.
  • 14 in. by 10 in. with a max. depth of 1.75 in.
  • 22 in. by 14 in. with a max. depth of 0.75 in.

In general, tolerances of ±0.005 in. are expected and achieved on well-design machined parts.

Magnesium Injection Molding
If you are looking for quantities of up to 5,000+ magnesium parts, magnesium injection molding (also known as thixomolding) is available. This process produces net-shape part with minimal porosity (fully dense) that are comparable to large-scale production parts. You can get injection-molded parts in magnesium AZ-91 in 15 days or less. Maximum part size for magnesium injection molding is 11.5 in. by 9 in. by 4 in. with tolerances of ±.0005 in. plus ±0.001 in./in.

Injection-molded magnesium parts are removed from the press and require secondary finishing to remove excess material.

Other Considerations
As with all magnesium, the part can show signs of surface corrosion and we strongly recommend secondary finishing (outside of Proto Labs) such as e-coat, powder coat, painting and anodizing in order to preserve the parts.

Magnesium is flammable, but don’t be alarmed. Magnesium is primarily flammable in molten form or with fine metal shavings when extreme heat and flame are present. It is extremely difficult to ignite solid magnesium. Coating mag parts with the aforementioned techniques will bring additional protection not only from corrosion but also ignition.

For more information on magnesium, check our complete CNC machining and magnesium injection molding design guidelines, or contact one of our customer service engineers at or 877.479.3680 with questions or concerns.

This entry was posted in Tips with Tony and tagged , , , , by Tony Holtz. Bookmark the permalink.

About Tony Holtz

Tony is a technical specialist at Proto Labs with more than 10 years of experience ranging from CNC mill operator to mold designer to customer service engineer. While his formal education is in industrial machinery operations, he has extensive knowledge and experience in both traditional and advanced manufacturing processes and materials. Throughout his tenure at Proto Labs, Tony has worked with countless designers, engineers and product developers to improve the manufacturability of their parts.

Leave a Reply

Your email address will not be published. Required fields are marked *


You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>